The standard external quantum sensor (LI-190R) provided with the LI-6800 sensor head (LI-6850) has a 12 inch (30.5 cm) cable terminated with a 3.5 mm audio plug. For some applications, it may be desirable to place an external quantum sensor at a greater distance from the sensor head. For these applications, an audio plug adapter can be used in conjunction with another LI-190R quantum sensor with a longer cable. LI-190R sensors are available in cable lengths of 2m, 5m, 15m and 50m.
An audio jack to bare leads (LI-COR part # 9968-158) will connect to a quantum sensor with a longer cable (Figure 1). For connecting to a bare lead quantum sensor, simply connect the red wire to the brown wire on the sensor, and white to blue. When using with an LI-190R terminating in a BNC connector, a female BNC connector will be needed. These are readily available in most locations, but can also be ordered from LI-COR (part # 312-00596). If using this female BNC connector, we would also recommend ordering a threaded tube (part #6501-080) for strain relief. After soldering the wires and installing the tube, filling the tube with epoxy will provide additional strain relief. Epoxies can be readily obtained from most hardware stores.
When switching between different quantum sensors, be sure to enter the correct calibration multiplier on the LI-6800. This is done through the Chamber Settings page in the StartUp->Configurations Tab (Figure 2). Calibration multipliers for LI-190R quantum sensors can be obtained from our website https://www.licor.com/env/support/ by entering the serial number in the ‘Looking for your Calibration Certificate?’ window on the right-hand side of the page.